LindowsOS 4.5 Includes Integrated Free SIP Softphone

The latest release of the Lindows.com operating system (LindowsOS 4.5) includes an integrated SIP softphone client from Xten for calling on the SIPphone network. LindowsOS 4.5's X Lite Plus softphone combined with the SIPphone network gives the user a unique number from which to send and receive calls; it also includes four-way conferencing abilities, as well as 800 number access from any location worldwide.
http://www.xten.com